1. Field of the Invention
The invention pertains to apparatus for coupling optical components and more particularly to the coupling of a single optical fiber to electro-optic conversion means.
2. Description of the Prior Art
Coupling of energy in the visible or near visible light spectrum, herein referred to as optical energy, from a fiber optic transmission line terminal to an electro-optic conversion device normally contained within a hermetically sealed container, such as a hybrid electronics package, in a convenient yet efficient manner presents a number of unique problems that have not been solved economically by prior art coupling mechanisms. Included in these problems is the beam divergence associated with a large separation between the fiber end and the conversion device. These problems are aggravated when a single fiber transmission line is employed. One prior art structure includes a light energy transparent window hermetically sealed in the hybrid package wall with an optical line terminal receiving plug on the outside of the package and a stub line on the inside aligned with a conversion device, usually supported on the hybrid circuit substrate, through an alignment device such as a "V" block. While such an arrangement provides good hermeticity, it presents problems, such as coaxial alignment of the optical lines and beam divergence between the ends thereof, which limit optical coupling efficiency. Alternatively, the fiber optic line itself was passed through an opening in the package sidewall and sealed thereto. While this eliminated the alignment and divergence problems, it presented hermeticity problems. Another technique involved the use of micropositioners to precisely align the fiber terminal with the electro-optic conversion device mounted on the hybrid substrate through an opening in the hybrid package to obtain maximum coupling efficiency and then sealing the terminal in the opening. While this procedure maximizes efficiency, cost is increased and hermeticity reliability is reduced. In these prior art devices the electro-optic devices are usually mounted on or carried by the circuit substrate independent of the fiber coupling means or support making it difficult and expensive to provide coupling efficiency and hermeticity. Other prior art coupling techniques involve the use of collimating lenses but costs and alignment constraints render such techniques impractical. The present invention overcomes the foregoing disadvantages of the prior art and achieves a highly efficient optical coupling without jeopardizing the hermeticity of the hybrid circuit package. The invention further achives these advantages without complex and expensive fixtures and with standard hybrid circuit package manufacturing techniques.